Connecting The Gas Supply - Micromeritics FlowSorb III 2305 Operator's Manual

FlowSorb III

Connecting the Gas Supply

A variety of gas mixtures may be employed as described in Appendix B. The
most common for single-point surface area evaluation is a mixture of 30% nitro-
gen and 70% helium. Several mixtures containing between approximately 5 and
24% nitrogen are required when making multipoint surface area analyses. Pre-
mixed gases are conveniently employed for single-point and multipoint surface
area measurements. A Multigas Manifold is recommended for performing
multipoint analyses (refer to Chapter 5 for ordering information).
Whatever the gas mixture or its source, it should be regulated to a pressure of at
least 0.11 MPa (15 psig) by a reliable, leak-tested regulator. Suitable regulators
are available from Micromeritics (refer to Chapter 5 for ordering information).
Some commercial regulators incorporate internally a lubricant that can mi-
grate and contaminate downstream systems. These types must be avoided.
One regulator is required to make single-point tests. As many as four can be used
to make multipoint analyses with pre-mixed gases. Micromeritics uses and recom-
mends the use of research-grade gases. If unobtainable, the highest purity gas con-
veniently available will probably prove satisfactory. Since the same gas is
employed in calibration as in making measurements, small proportions of such
gases as argon, carbon dioxide, carbon monoxide, and methane will have an insig-
nificant effect on results. Water vapor, however, is particularly degrading; gas hav-
ing a dew point of at least -67 °C (-88 °F) should be sought.
Appendix C lists addresses worldwide of one specialty gas source as supplied by
that company.
Connect the gas supply as follows:
1. Attach an appropriate regulator to the gas bottle. Leave the gas bottle shut-
off valve closed until instructed otherwise.
2. If the regulator has a 1/8-in. outlet, proceed to the next step. If the regulator
has a 1/4-in.outlet, attach the reducer fitting to the outlet of the regulator
shut-off vlave.
Aug 00
Connecting the Gas Supply
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